Having finally finished preparing my 2010 income tax filing, I was thinking about taxes and politics. I thought of a social/political experiment that would be really interesting. I don't expect to see it happen in the real world, though science fiction authors could expand on it in either utopian or dystopian stories.
The basic idea is simple: allow taxpayers to specify where their money can be spent.
The implementation of the idea would be a bit complicated, and societal safeguards would make it even more complicated.
The simplest form of implementation would be for every personal income tax filing to include a set of check-boxes for government departments. That filer's money could only fund the departments the taxpayer checked.
A slightly more elaborate version would allow the taxpayer to specify percentages of their taxes to go to each department.
A variation might allow taxpayers to address social issues like family planning and honest sex education. Pro-choice taxpayers could designate funding for those purposes and anti-choice people could ensure that THEIR money wasn't paying for them.
Allowing taxpayers to say how their money should be spent would remove the huge "taxation without representation" problem created by our current political structure.
It would also reverse the current corrosive effect of corporate money on politics, if only REAL PEOPLE could specify how their taxes should be used. Since I'm imagining this, the option to specify would only be offered for personal income taxes, not corporate.
Having lived in California for quite a few years, I'm aware of deep flaws in the initiative process that has constrained large parts of the California budget based on popular votes, so I realize there would need to be safeguards in any system of popular control of funding. The basic flaw in popular control is that too many people make uninformed votes that are swayed more by well-funded advertising campaigns than by facts.
My first thought for a safeguard is a delay loop to prevent wild fluctuations. Rather than changing the funding of all government functions based on the filings of a single year, funding would incorporate a moving average of several years. The government would have to be totally open about what the funding of each department pays for, and inform the population each year what services would gain or lose based on the "tax vote".
I don't know if people would act wisely enough for such a system to work (hence the possibility of both utopias and dystopias), but it would certainly be an interesting change from the current mess.

The basic idea is simple: allow taxpayers to specify where their money can be spent.

This could NEVER work because the average citizen doesn't have thorough knowledge of what taxes actually pay for. It goes WAY beyond welfare and food stamps.

For instance, taxes pay for building codes and inspectors to ensure that residential and commercial buildings are built safely, with some measure of fire resistence, wind-resistence, insulation, stability, etc.

How do you separate that out? I guess the buildings could come with some sort of sign or symbol that indicates which ones are built to code and which ones are not, which ones were inspected and which ones were not. What then would happen is that the "haves" (who have ample financial resources) would be living in the inspected/built-to-code buildings while the "have-nots" would be living in the non-inspected/not-built-to-code buildings.

(And human nature being what it is: Iin order to ensure the ongoing separation -- so that the "haves" don't have to share their space with the "have-nots" -- the prices on the buildings built to code would be substantially higher than the prices on the others. Kind of like today's gated community neighborhoods. Unless of course there were regulations in place to prevent that kind of pricing abuse. Of course, regulations are paid for with taxes.....)

Similarly.... Taxes support the statutes that ensure that a gallon of gas truly IS a gallon. That's why the pumps are inspected every year, so that consumers can rest assured that they're paying for 10 and getting 10...not paying for 10 and getting 8. So say that John Q. Taxpayer decides that he wants his tax dollars to support the ongoing regulations of the gas pumps. Yay for John. But how does he guarantee that he's always going to have those assurances in place. Sure, where he lives, he's likely to have his choice of pumps that are "legit." But what if he's traveling and winds up in Podunk where the people are too poor to allocate their tax dollars for weights-and-measures statutes. Now he's just screwed. (One could also hope that the taxpayers in Podunk cared enough to invest their tax dollars in road maintenance and infrastructure, or John's might have to leave his muffler on the rutted road behind him....)

Then let's get into "comingled" elements like air and water. Say that one city's taxpayers decide that the preservation of their environment is important to them, so they allocate their tax dollars to go toward environmental protections and resource management. But the city 100 miles down the road DOESN'T choose to allocate their tax dollars similarly. How does City A maintain fresh air and clean water, etc. when City B, whose streams and air flow into City A, isn't equally motivated?

One tax I would like to see is the Plastax, a fee for using plastic bags. Ireland charges $.33/bag! I have heard more in the range of $.05/bag here in the US. The idea is to discourage the use of disposable bags and instead have people reuse their bags (cloth or straw) and containers.

In response to your thoughts about people getting to choose how their tax dollars are spent, please consider an example concerning the EPA. The EPA ranks indoor air pollution as one of their top concerns for public health while the average citizen is not even aware its a problem.

[This could NEVER work because the average citizen doesn't have thorough knowledge of what taxes actually pay for. It goes WAY beyond welfare and food stamps.

It sounds like you're saying that the public may be smart enough to earn the money, but not to say how it should be spent. I think the 'average citizen' understands the need for safety inspections, weights and measures regulation, and clean water--and many would choose those options over, say, another pay increase for Congress, another Wall Street bailout or another illegal war. As it stands now, we have virtually no one representing our interests and a whole slew of people representing the oligarchs--while making fortunes off insider trading (see today's Washington Post) which is legal because congress is not subject to the same laws as the rest of us poor suckers.

Also, if you're implying that our reps have a 'thorough knowledge' of what taxes actually pay for, I suggest you watch clips of some of them trying to answer very basic questions about our government. Their ignorance is staggering.

It would be very interesting to at least try this as a test and see what the American people would choose to fund with their money.